Nematodes, which are unsegmented roundworms with elongated, fusiform, or saclike bodies covered with cuticle, are virtually ubiquitous in nature, inhabiting soil, water and plants, and are importantly involved in a wide range of animal and plant parasitic diseases. Infections with gastro-intestinal nematodes are a major constraint on ruminant (cattle, sheep, goats, etc.) welfare and production worldwide. Infections with these parasites can lead to severe disease (diarrhea or anemia are typical symptoms). Among the economically important effects on livestock are reduction in milk, meat and wool production, weight gain and occasional death.
Important trichostrongylid parasites in cattle (bovine) are Cooperia oncophora, C. punctata, C. pectinata, C. curticei and Ostertagia ostertagi. In small ruminants, e.g. sheep and goats, infections with Haemonchus contortus and Teladorsagia circumcincta are the most important. Although being regarded as a mild pathogen, the helminth Cooperia oncophora is one of the most common intestinal parasitic nematodes in cattle in temperate climate regions worldwide (1) and as such carries a substantial economical footprint as it holds a profound share in production losses (2, 3). A recent study demonstrated that helminth infections increase United States beef production costs by nearly $190 per head according to 2005 market prices (4). Analogous to the use of antibiotics in humans, anthelmintics have long been the method of choice to treat and prevent parasite infections in a reasonably efficient and low-cost manner. For use in cattle, three major classes of anthelmintics are currently available, i.e. imidazothiazoles, benzimidazoles and macrocyclic lactones, the latter being the most frequently used in Cooperia oncophora treatments. However, the downside to this medal has gradually become apparent during the last decade as numerous reports of developing anthelmintic resistance have surfaced throughout the world (5-9). In addition, there is a concern regarding drug residues in meat and the environment. More effective avenues in controlling helminth infections are therefore highly necessary, one of which may involve the development and administration of prophylactic vaccines.
Since the issues surrounding anthelmintic resistance are observed for a multitude of helminths, numerous research groups have invested in the development of recombinant vaccines for e.g. Ancylostoma caninum (10), Onchorcerca volvulus (11-14), Ascaris suum (15-17), Haemonchus contortus (18, 19), Necator americanus (20), and several Taenia (21-23), Echinococcus (21, 22), Fasciola (24) and Schistosoma (25-30) species. However, the efficacy of these vaccines, measured as reduction of egg counts and/or worm burden (reviewed in (59)), was found to vary dramatically and is thus unpredictable.
Currently, no Cooperia oncophora vaccine exists. Several research groups have focused on the low-molecular weight proteins (12-16 kDa) as potential vaccine candidates, however without success (60-61; WO98/01550).